Camshaft adjusters are used in internal combustion engines to vary the timing of the combustion chamber valves so that it is possible to vary the phase relation between a crankshaft and a camshaft within a defined angular range, between a maximum early and a maximum late position. Adjusting the timing according to the actual load and rotation speed reduces fuel consumption and emissions. For this purpose, camshaft adjuster are integrated into a drive train, which a torque is transmitted from the crankshaft to the camshaft. This drive train may be designed as e.g. a belt, chain or gear drive.
In a hydraulic camshaft adjuster, the output element and the drive element form one or more pairs of mutually acting pressure chambers, which can be pressurized by use of hydraulic fluid. The drive element and the output element are arranged coaxially. By filling and emptying individual pressure chambers, a relative movement between the drive element and the output element is generated. The spring, which is rotatively issuing its force between the drive element and the output element, pushes the drive element into an advantageous direction in relation to the output element. This advantageous direction can be the within the same, or opposite to the rotation direction.
One construction type of a hydraulic camshaft adjuster is the vane cell adjuster.
The vane cell adjuster comprises a stator, a rotor and a drive wheel with an external toothing system. The rotor is mostly designed as the output element in such a way that it can be coupled to the camshaft for joint rotation. The drive element comprises the stator and the drive wheel. The stator and the drive wheel are coupled for joint rotation or are alternatively designed as one piece. The rotor is arranged coaxially towards the stator and within the stator. The rotor and the stator with their vanes, which extend radially, create oil chambers that operate in a contrary manner, which can be pressurized by using oil and allow for a relative rotation between the stator and the rotor. The vanes are either designed together in one piece with the rotor or the stator or are arranged as “inserted wings” within designated slots of the rotor or the stator. The vane cell adjusters furthermore comprise various sealing lids. The stator and the sealing lids are secured together by multiple screw connections.
Another type of a hydraulic camshaft adjuster is the axial piston adjuster. An adjusting element is hereby axially moved by using oil pressure, which generates a relative rotation between a drive element and an output element via helical gears.
A further design-form of a camshaft adjuster is the electromechanical camshaft adjuster, which comprises a three-shaft gearbox (for example, a planetary gearbox). One of the shafts hereby forms the drive element and a second shaft forms the output element. Rotation energy can be supplied to or dissipated from the system via the third shaft by using an adjusting device such as an electric motor or a brake. A spring can be additionally arranged, which supports or resets the relative rotation between the drive element and the output element.
The DE 100 62 184 A1 shows a spiral torsion spring of a camshaft adjuster. Both ends of the spiral spring are radially bent towards the outer side. The first bent end rests on a fixed pin that protrudes from the chain sprocket, and the second bent end rests on a pin that protrudes from a vane gate. The spiral spring is pushing the vane rotor in such a way, that the vane rotor is hurrying ahead in relation to the chain sprocket. This means that the spiral spring is pushing the vane rotor to such an extent, that one camshaft is hurrying ahead in relation to a motor crankshaft.
The DE 10 2006 004 760 A1 shows two springs in two pressure chambers of a camshaft adjuster, wherein there is one respective spring in each pressure chamber that pushes on the vane and correspondingly causes an adjustment from the direction “early” or “late”.
As shown in FIG. 16A and FIG. 16B, the EP 2 302 177 A1 shows a spring, which can push the rotor in relation to the stator into an angular position for the combustion engine in the case when there is a pressure drop in the pressure chambers, so that it can be started again.